The structure, function and expression of keratin intermediate filaments of human skin, and the related intermediate filament proteins of other cell types are being investigated. These studies are designed to understand the structural features which determine how the rod domains of the constituent coiled-coil molecules pack together to form the core of the filament, and how the protruding end domains define filament function. Having recently developed detailed models on probable molecular packing, we have constructed a series of synthetic peptides corresponding to important molecular overlap regions for the purpose of X-ray crystallography to solve three dimensional structures. Several of these peptides have been micro-injected into living cells in order to explore their dynamic behavior. In order to explore the functions of end domain sequences, we have constructed another series of peptides to structurally interesting portions of vimentin to explore their protein interactions by way of the yeast two hybrid system. In other studies, we have determined that a portion of the V1 region of the type II keratins 1, 2e and 5 is involved in crosslinking with other proteins to the cornified cell envelope, a process which is likely to provide a mechanism by which the keratin intermediate filament cytoskeleton is anchored to the cell periphery. Analysis of other crosslinks reveals that the keratin chains may also be attached to the desmoplakin component of desmosomes indirectly by way of an intermediate filament associated protein. Epidermal keratinocytes obtained from a patient with epidermolytic hyperkeratosis with a keratin 10 gene mutation have been virally transformed. The cells express both the normal and mutated alleles. This cell line will now be very useful to test gene therapy approaches.